Utilizing spent pickle liquor.



No. '788.064- PATENTED APR. 25, 1905. A. S. RAMAGE.

UTILIZING SPEN'I PICKLB LIQUOR. APPLICATION FILED JAN.31,1905.

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Patented .April 25, 1905.

PATENT @Price ALEXANDER S. RAMAGE, OF DETROIT, MICHIGAN.

UTILIZING SPENT PICKLE LIQUOR.

SPECIFICATION fOlming part of Letters Patent No. 788,064, dated April 25, 1905.

Application filed January 31,1905. Serial No. 243,558.

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Be it known that l, ALnxAND un S. RAMAGE, a citizen of the United States, residingl at Detroit, in the county of rayne and State of Michigan, have invented certain new and useful Yimprovements in Processes of Utilizing Spent Pickle Liquor, of which the following is a specification.

This invention is a method of treating spent sulfuric-acid pickle liquor to recover metal and regenerate the liquor.

The invention will be described as applied to the utilization of ferrous sulfate liquors Vfrom the pickling of iron, but is also applicable to metal-bearing solutions obtained by pickling copper and other metals.

l prefer to proceed as follows: The pickle liquor containing ferrous sulfate and free sulfui-ic acid, the latter in quantity insufficient for economical pickling, is saturated with sulfur dioxid, preferably in a suitableabsorptiontower, and then conducted through closed electrolytic vats each provided with anodes of lead and cathodes of iron. 1n these vats iron is deposited in a state of substantial purity on the cathodes, while free sulfuric acid accumulates in the electrolyte. The regenerated liquor is freed from any remaining sulfur dioxid by heat and again utilized in the pickling process. It is not economical to continue the piekling until all free acid is combiiied by reason of the slow action of weak liquors, nor, on the other hand, is it desirable to continue the electrolysis until allof the combined acid is liberated, by reason of the low efiicieneyof deposition 'fromdilutemetalbearing solutions. I prefer, therefore, to so regulate the process that both pickling and electrodeposition are rapidly and economically effected. I do not limit myself to any specific proportions of acid or of metal in the liquor at any stage of the process; butl have found it practicable to continue the pickling until the freeacid content is reduced to onehalf to one and one-half per cent., and thereafter to continue the electrolysis until the free acid is increased to five to fifteen per cent. The function of thesulfurdioxid is threefold. First, by its oxidation it yields sulfuric acid, thereby increasing the free-acid content of the liquor at a greater rate than corresponds to the deposition of the metal; second, it provides the excess of sulfuric acid required to prevent the precipitation of basic sulfate of iron, which would quickly interrupt the electrolysis were it attempted to directly electrolyze the pickle liquor, and, third, it serves to reduce the electromotive force required for the electrolysis, as is well understood in connection with the deposition of metals.

An arrangement of apparatus suitable for carrying out my process is shown in the accompanying drawings, wherein-"- Figure l is an elevation, partly in section, of the apparatus for treating pickle liquors; and Fig. 2 is a vertical longitudinalsection of one`form of electrolytic vat.

l represents a storage-tank forspent pickle liquor, and 2 3 a pipe and pump for transferring the liquor to an absorption-tower This tower may be of any suitable type and is preferably filled with coke, over which the liquor is distributed b v a reaction-mill or other suitable device 4.

G represents the inlet for sulfur dioxid or for a mixture ofsulfur dioxid and air in case it is desired to take advantage of the formation of sulfuric acid by the oxidation of sulfui' dioxid in the absorption-tower.

The acid liquor containing sulfuric and sulfiirous acids and ferrous sulfate is permitted to fiow through pipe T into a reservoir 8 and is thence carried through pipe 9 and pump l0 to a supply-tank l1, which is connected through pipe l2 with a series of covered electrolytic vats 13. ln these vats metal is deposited and free acid formed, as above described, and the resulting regenerated liquor is permitted to overfow into a tank '14, fi'om which it is withdrawn for further utilization in the pickling of metal. Tank l- L is preferably provided with a heating-coil l5, whereby any dissolved sulfur dioxid may be expelled through outlet 1G to be returned to the tower 5.

The electrolytic vats are preferably so constructed as to provide a tortiious fiow of the electrolyte successively past anodes 2l 22 and cathodes Q3. As illustrated, each electrolytie vat 13 comprises a body 17 and a lining 20, which is preferably of lead and in electrical connection with the anodes 21 22, the latter consisting of partitions extending transversely across the vat. The vats are mounted at a slight inclination, and the transverse anode-plates 21 22 are so disposed that the liquor may pass alternately above and below successive anode-plates. The cathodes 23, which may be of iron, depend between the anodes and are preferably supported by and in electrical connection with the metallic cover 18, insulation 19 being interposed between the cover and the body of the vat.

I claim- 1. rlhe process of utilizing spent sulfuricacid pickle liquor, which consists in dissolving sulfur dioxid in the liquor, electrolyzing the resulting solution with insoluble anodes, thereby depositing metal at the cathode, and freeing the combined acid'and oxidizing the dissolved sulfur dioxid at the anode, and employing the regenerated liquor to pickle metal` substantially as described.

2. The process of utilizing spent sulfuricacid liquor from pickling iron, which oonsists lin dissolving sulfur dioxid in the liquor, electrolyzing the solution with insoluble anodes, thereby depositingiron at the cathode and freeing the combined acid and oxidizing the dissolved sulfur dioxid at the anode, and employing the regenerated liquor to pickle iron, substantially as described.

3.. The process of regenerating spent pickle liquors containing ferrous sulfate, which consists in dissolving Sulfur dioxid in the liquor, and electrolyzing the solution with insoluble anodes, thereby depositingiron at the cathode and freeing the combined acid and oxidizing the dissolved sulfur dioxid at the anode, substantially as described.

In testimony-whereof I aflx my signature in presence of two witnesses.

ALEXANDER S. RAMAGE. l/Vitnesses:

IRVING W. DURFEE, F. A. PLATT. 

